Figure 2.

Passive and active tumor targeting. Passive tumor targeting is the extravasation of NM due the increased permeability of the tumor vessel together with a lower lymphatic drainage. This is also known as the EPR effect. Active cellular targeting is the surface functionalizing of NM with ligands to induce cell-specific recognition and binding. The contents of the NMs can be released close to the target cells (i), act as an extracellular release drug depot by attaching to the cell membrane (ii) or can also internalize into the cell (iii). Reproduced with permission from ref (11). Copyright 2007 Nature Publishing Group.